Electronic devices are used for communication, as storage for information and photographs, and to conduct business and financial transactions. Because of the wide range of uses, the power required to keep a screen illuminated, and the amount of information stored on the electronic devices, many electronic devices turn off the screen and lock themselves after some time period without active user interaction or based on some other criteria. Once the electronic device is locked, typically only an authorized user can unlock and access the device. Electronic devices therefore also typically include technology that allows the device to authenticate a user (e.g., determine that the user is an authorized user) before granting the user access to the device.
Depending on how long the user accesses the device per session or how often the user interacts with the device, users may have to be authenticated multiple times each day (according to some studies, typical users access their electronic devices more than 50 times per day). Often, authentication requires the user to perform a particular interaction on a touchscreen, remember and enter a complicated password, or hold a finger against a sensor long enough for the device to detect a fingerprint.